The U.S. Pat. No. 2,188,162, Schulhoff, describes a sewage treatment system for biological clarification and purification of sewage by the action of aerobic bacteria. The system includes submerged bundles of tubes on which colonies of aerobic bacterias are formed which are active in decomposition of organic matter contained in sewage. The system includes means for discharging compressed air in finely divided condition into the sewage near the bottom of the tank to furnish the oxigen required by the aerobic bacterias. The patent does not disclose the use of the system for anaerobic decomposition and does not provide means for preventing the clogging of individual tubes.
The German published patent application 24 20 745, to which U.S. Pat. No. 4,045,344, YOKOTA, corresponds, discloses a sewage treatment system with a submerged bundle of tubes or ducts, but provides over the length of a duct a plurality of interconnections with other ducts with the purpose to cause turbulent flow in the ducts. Nozzles are provided to feed air into the sewage to provide for aerobic digestions. It does not disclose anaerobic digestion and means for declogging the ducts.
The published U.K.-patent application No. 2 069 929, Witt, discloses an anaerobic reactor apparatus comprising a sealed vessel containing a packed section filled with a support packing on the surface of which packing is a biomass of microorganisms capable of biologically degrading the organic contents of the liquid waste water. A pump is provided to pump the liquid underneath the packed section, so that the liquid level is always beneath the packed section. The packed section consists of plastic rings or old aluminium cans through which the liquid may trickle. The published application does not disclose the use of the reactor for the treatment of sludge, nor does it show means to prevent clogging, which is a problem when treating sludge.